login
A113595
Least multiple of n which is greater than n and is a concatenation of two successive natural numbers k and k+1.
2
12, 12, 12, 12, 45, 12, 56, 56, 45, 910, 1617, 1920, 78, 56, 45, 1920, 34, 1314, 2223, 1920, 1617, 2728, 2829, 1920, 2425, 78, 3132, 56, 3132, 1920, 2728, 1920, 1617, 3536, 910, 3132, 2627, 4142, 78, 1920, 2829, 3738, 2021, 2728, 4950, 5152, 2021, 1920, 1617
OFFSET
1,1
COMMENTS
'Multiple' means >1 and the concatenation is left-to-right only.
MATHEMATICA
Module[{nn=99, cc, t}, cc=Table[FromDigits[Flatten[Join[ IntegerDigits/@ {n, n+1}]]], {n, nn}]; Table[t=Select[cc, Divisible[#, x]&]; If[t[[1]]>x, t[[1]], t[[2]]], {x, 50}]] (* Harvey P. Dale, Sep 17 2020 *)
PROG
(Python)
def a(n):
k, concat = 1, 12
while concat <= n or concat%n:
k += 1
concat = int(str(k)+str(k+1))
return concat
print([a(n) for n in range(1, 50)]) # Michael S. Branicky, Dec 12 2021
CROSSREFS
Cf. A111381.
Sequence in context: A302341 A064162 A028996 * A109053 A186100 A376818
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 07 2005
EXTENSIONS
Corrected and extended by Hans Havermann, Nov 08 2005
Definition clarified by Harvey P. Dale, Sep 17 2020
STATUS
approved